Hi I’m in the process of doing a simple prototype of a gas pressurized liquid propellant engine. I’m trying to do the prototype using off the shelf parts as much as possible to keep costs down. One component I’m having trouble finding off the shelf is a tank for pressurizing fuel or oxidizer with two valves: one at the top and one at the bottom. Most tanks, such as a propane tank for bbq’ing or a kerosene tank used for a camp stove have a single valve at one end that can be used for either pressurizing or releasing gas. This would be similar to a blowdown tank configuration where the pressurizing gas is stored inside the tank. That configuration doesn’t work so well because as the fuel is expelled the pressure decreases.

So I’m wondering if you could recommend any places to get a small’ish tank that has 2 valves: 1 at the top for inputting a pressurizing gas and another at the bottom for releasing the fuel or oxidizer towards the thrust chamber?

I suggest using a common propane tank and drilling a hole in the bottom and welding in a suitable bung. I highly recommend hydro testing to three times operationg pressure testing with pressurized water instead of a gas) before pressurizing with a gas.

If you really trust your welding you can add a section to a common grill size tank and hold more fuel/oxydizer. These tanks are made of mild steel but annealing the weld is always a good idea.

REMEMBER THE FIRST RULE OF ROCKETRY: NEVER, EVER TEST A ROCKET INSIDE A BUILDING.

SECOND RULE: NEVER BE CLOSER THAN THE RANGE OF THE SHRAPNEL CREATED BY THE INEVITABLE EXPLOSION. See rule #1